1-4 The Evolution Of Plants

It's quite a simple structure and you find things that look much like modern pine trees stretching back hundreds of millions of years in the evolutionary record.

I've come here because it's the perfect place to illustrate how plant evolution began. Now the very first plants to emerge onto land were descendants of algae that developed roots that allowed them to attach to the ground and spread into soil. And they were probably things much like our ferns in the modern world.

So ferns are the beginning of plants. The next major innovation though was developing seeds, which are quite a useful thing for plants to be able to do because seeds carry nutrients with them, they're storage organs so that you make sure your offspring when they land somewhere they already have a large proportion of the resources they need to establish themselves. And they can also be maintained for much longer so they can stay in the soil or they can be carried around by animals.

The first major division of plants then is between the seed-bearing plants called the Pinophyta or the gymnosperms and the flowering plants called the Magnoliophyta or the angiosperms.

Now the difference between the two of them is down to how they produce their seed. The ancestral form, the oldest types, are the gymnosperms. And that comes from the Greek for gymno which means naked in the same way as the gymnasium was the place where Greek people did their sports in the buff and sperm meaning seed.

Gymnosperms produce their seeds in cones. You'll be familiar with this from any pine tree. And what typically happens is that you'll see along the sides of this cone you've got an array of slits in it, each one of which will have held a seed which when it's mature will have dried and fallen out and then hopefully gone on to germinate somewhere afterwards.

The real innovation though came when plants instead of producing seeds just naked and falling straight off the plant started to wrap them in something. And this is why we refer to them as the angiosperms. Angio comes from the Greek angion meaning vessel. It means the seed is stuck inside something.

Now this is a major innovation because as soon as you've wrapped the seed in something it's more protected, it's got a shell, it's going to be kept moist, but you can also attract animals. And the angiosperms started to spread and to become important when animals were able to eat those seeds and move them around and disperse them. At the same time the angiosperms came up with a whole new innovation which was the flower and that's why we tend to refer to them as the flowering plants.

But the really first group of plants that showed the sorts of flowers and structures that we're used to now were the magnolias. And here we have a magnolia tree. This is the perfect season to look at them. I love magnolias and I especially love this time of year because when the magnolias come into flower they're just this massive exuberant color. They're crazy brilliant gaudy trees. And we can tell their early part in the evolutionary history of flowers because these flowers are really quite disorganized. They've just got this jumble of petals thrown together in the brightest largest size you can imagine. In the middle you have the flowering parts. You have your standard parts of a flower so you've got the male parts, the anthers here in purple, and the female parts, the green parts there, so the stigmas which receive the pollen and produce the seeds afterwards.

One of the earliest groups of flowers is this similarity here. If you look at that central spike there it is basically a pine cone stuck in the heart of a flower with multiple sections each of which will produce a single seed. And if you see a magnolia after it's flowered when it comes into fruit what you find is something that looks remarkably like this cone.

So it looks almost the same as a pine cone except for the fact that the seeds are wrapped in something. They're angiosperms. They have this fleshy fruit around them that the birds will then eat and carry the seeds elsewhere.

And this is a species I haven't identified yet but it's from the Orobanchaceae which is a family of parasitic plants that don't have any of their own chlorophyll but they attach themselves to the roots of other plants and produce these flower stems.